Ab initio study of angle-resolved electron spectroscopy of graphene

0568482 - ÚPT 2023 RIV CZ eng A - Abstrakt
Paták, Aleš - Zouhar, Martin - Konvalina, Ivo - Materna Mikmeková, Eliška - Průcha, Lukáš - Müllerová, Ilona - Charvátová Campbell, A.
Ab initio study of angle-resolved electron spectroscopy of graphene.
16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts. Brno: Czechoslovak Microscopy Society, 2022 - (Krzyžánek, V.; Hrubanová, K.; Hozák, P.; Müllerová, I.; Šlouf, M.). s. 156-157. ISBN 978-80-11-02253-2.
[Multinational Congress on Microscopy /16./. 04.09.2022-09.09.2022, Brno]
Grant CEP: GA TA ČR(CZ) TN01000008
Institucionální podpora: RVO:68081731
Klíčová slova: density-functional theory * low-energy electron microscopy * many-body perturbation theory
Obor OECD: Electrical and electronic engineering
https://www.16mcm.cz/wp-content/uploads/2022/09/16MCM-abstract-book.pdf

Since the discovery of graphene in the first decade of the 21st century, this material and 2D-materials in general have attracted great attention due to their particularly distinctive properties. The corresponding scientific effort led to new and unexpected results, e.g. magic angle twisted graphene exhibiting superconductivity in the case of twisted bilayer graphene (TBG). The potential industrial and commercial applications are immense. These materials are studied using many techniques, including e.g. optical microscopy, Raman spectroscopy, atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) have been used to distinguish the number of graphene layers, their stacking order and twist. STM, TEM and EELS can provide a very good resolution and characterize these materials locally. Measurements at high TEM energies have destructive effects, due to knock-on damage, on the samples and hence it is desirable to decrease the energy of incident electrons. In order to quickly assess larger areas, scanning electron microscopy (SEM) represents a reasonable compromise - scanning larger areas with sufficient resolution. This includes both imaging and collecting spectra. The above overview makes clear that electron microscopy is one of the important tools utilized in the studies of these materials. Theoretical investigations, e.g. ab initio simulations, may provide worthy insight into experimental results. We present the theoretical results obtained using the density-functional theory (DFT) and the many-body perturbation theory (MBPT). They include low energy momentum-resolved both reflectivity and EELS spectra, the first with phenomenological inclusion of inelastic effects. The EELS spectrum of graphene is shown in Fig. 1. A part of this spectrum was used to examine the momentum transfer present in our time-of-flight experiment already. Furthermore, the theoretical simulations considered here predict that the Moiré patterns in TBG (typically accessible via STM) should be observable even in SEM equipped with a cathode lens (stage bias). We predict that SEM is able to provide valuable spectroscopic information about unoccupied band-structure of 2D materials. Moreover, our findings imply that SEM at low landing energies should be able to display Moiré super-lattices. This significantly expands the class of electron microscopes that can be used to study and assess quality of these extremely interesting materials.
Trvalý link: https://hdl.handle.net/11104/0339786